1. Technical Field
The present invention relates to a method for manufacturing a nozzle substrate for discharging ink or another liquid, and a method for manufacturing a droplet discharge head provided with the nozzle substrate.
2. Related Art
There is a conventionally known droplet discharge head for discharging droplets that has a layered structure in which the following three substrates are superimposed in sequence: a nozzle substrate in which a plurality of nozzle holes for discharging droplets is formed; a cavity substrate in which a flow channel for a discharge chamber or the like for holding droplets and in which bottom surface constitutes a vibration plate; and an electrode substrate which is disposed facing the vibration plate via a gap and in which a discrete electrode for driving the vibration plate is formed. In this type of droplet discharge head, the nozzle substrate and the cavity substrate are ordinarily composed of silicon substrates, the electrode substrate is composed of a glass substrate, the nozzle substrate and the cavity substrate are bonded using an adhesive, and the cavity substrate and the electrode substrate are bonded using anodic bonding.
In recent years, the range of use of droplet discharge heads has expanded beyond document printing and photo printing to industrial and commercial uses. In accordance with this, various types of discharge fluids are used, and the properties of such fluids are varied. In a droplet discharge head having a layered structure, an adhesive is used for bonding the nozzle substrate and the cavity substrate as described above. Therefore, the adhesive dissolves into the discharge fluid and affects the discharge fluid, thereby limiting the physical properties of discharge fluids that can be used.
In view of the above, a nozzle substrate in which the cavity substrate can be bonded without the use of an adhesive has been proposed in the art (e.g., see Japanese Laid-Open Patent Application No. 2008-155591 (FIG. 2)). With this technique, the nozzle substrate is composed of a SOI layer (a configuration in which a silicon layer is bonded to the two surfaces of a silicon oxide layer), and the surface that bonds with the cavity substrate is the glass layer, thereby making anodic bonding with the silicon substrate possible.